Controllable force method and system of driving piles

ABSTRACT

A method and system for determining the magnitude of a driving force being exerted on a substantially rigid object being driven into the earth, such as a pile, and controlling the magnitude in response to that determination. Where the pile driver utilizes a massive piston weight reciprocating in a cylinder and bouncing upon pressurized fluid in a chamber, the force magnitude is determinable by sensing pressure values occurring in the bounce chamber. Force control is obtainable by regulating the flow of pressurized fluid into the bounce chamber in response to the determination. Peak pressure values are sensed by pressure gauge or transducer means to determine the peak values of driving force being exerted on the top of the pile and control of the pile driver operation can be manually or automatically obtained.

United States Patent Chelminski ]March 20, 1973 [54] CONTROLLABLE FORCE METHOD AND SYSTEM OF DRIVING PILES Primary Examiner-Emest R. Purser [75] Inventor: Stephen v. Chelminski, west Attorney-Bryan, Parmelee, Johnson & Bollmger Reddmg [57] ABSTRACT 73 I Asslgnee gg s Associates nc Norwalk A method and system for determining the magnitude of a driving force being exerted on a substantially rigid [22] Filed: Aug. 23, 1971 object being driven into the earth, such as a pile, and 21 A L N I 173 917 controlling the magnitude in response to that deter- 1 pp 0 mination. Where the pile driver utilizes a massive piston weight reciprocating in a cylinder and bouncing U-S- Clupon pressurized in a chamber the force mag- 173/131, 175/19 nitude is determinable by sensing pressure values oc- Cl. curring in the bounce chamben Force control is oh. [58] of Search ..6l/53.5; 173/ l 91, 5, tainable by regulating the flow of pressurized fluid into 173/139, 136, 137, 138, 131; 175/19, 56 the bounce chamber in response to the determination. Peak pressure values are sensed by pressure gauge or [561 References Cited transducer means to determine the peak values of UNITED STATES PATENTS driving force being exerted on the top of the pile and control of the pile driver operation can be manually or 3,314,241 4/1967 Mayhall ..173/1 X automatically obtained. 3,353,362 11/1967 Lubinski 3,417,828 12/1968 Duyster et a1. ..61/53.5 X 21 Claims, 4 Drawing Figures PATENTEDHmmm SHEET 4 0F 4 [LECTRO/Y/C CONTROLLER PRESS (IRE INTERMED/fl T' FL U/D RESERVOIR til II .SZe vizen V CONTROULABLE FORCE METHOD AND SYSTEM OF DRIVING PILES This invention relates to a method and system for determining and controlling the magnitude of the force exerted on a pile being driven into the earth.

Conventional pile drivers of the diesel or steam type use a falling weight or hammer strike down upon an anvil surface to transmit a blow to a pile. The forces on the anvil resulting from such a noisy striking type blow become destructive when the energy levels needed to drive a pile become high. In my co-pending patent application, Ser. No. 102,325, filed Dec. 29, 1970 for Automatically Self-Regulating Variable Stroke Variable Rate and Quiet Operating Pile Driver Method and System I describe a pile driver that overcomes the above and other disadvantages inherent in the conventional steam type of diesel type pile drivers and which has a massive piston weight that is bounced upon a cushion of pressurized fluid.

Previous methods and systems for driving piles using conventional type pile drivers have been ineffective in controlling the magnitude of the driving force being exerted on the pile being driven. This is due largely to the fact that the force on the pile has been measured or tested by inference, the standard procedure being to determine the load bearing capacity of a driven pile by reference to its resistance to be substantially further driven under a certain number of repeated blows by a particular size or weight of hammer. For example, one practice utilizing a prior art hammer calls for continued driving of the pile until its resistance to further driving requires delivering ten hammer blows to an inch of pile advancement. When the pile is being driven no faster than this rate, the desired load bearing capacity is assumed to have been obtained.

A disadvantage of the above manner of ascertaining the load bearing capacity by inference lies in the fact that the apparent resistance of the pile to further driving may be on the inability of the pile driver to drive the pile rather than on actual obtainment of the desired load bearing capacity. There are wide variations in soil conditions and in frictional effects which can occur between the earth and the side surfaces of a pile, and at the lower end of the pile various strata or rocks may be encountered. All of these variables can affect the pile driving operation. Unknown to the operator, the prior art driver may be malfunctioning so that it is not actually delivering its full rated blows. Thus, the pile would appear to be offering a certain resistance to further driving; whereas in fact the problem would be a lack of sufficient driving force. Later on, when a heavy structure is built upon the pile, it may sink down, causing damage to the structure above.

Another disadvantage of the prior art is. that the force applied to the top of a pile using prior art driving techniques may exceed the maximum force the pile is capable of withstanding and result in damage to the pile top or in weakening of the pile. Although some operators interpose wood blocks or the like between the driver and the pile to absorb excess force, such blocks readily became destroyed and required frequent replacement, causing delay, and their use represents a waste in energy. In effect, the prior art pile driving techniques leave the operator blind to what is actually occurring. He operates by inference and by experience, but unknown factors may be present which can lead to different results from what is contemplated.

The present invention overcomes these and other disadvantages associated with the previous methods and systems and provides a manner and means for determining the actual force being exerted on the pile as it is being driven so that is magnitude may be controlled at a predetermined level. Thus, it is an object of this invention to provide a method and system for determining and controlling the driving force applied to a pile and to enable the operator to stop driving the pile at a pre-determined force level.

A feature of this invention is that a massive piston weight is bounced up and down upon a cushion of pressurized fluid, the pressure of which is regulatable and is controlled. A further object of this invention, therefore, is to provide a method and apparatus for controlling the thrust generated by a piston weight bouncing on a pressurized fluid cushion by controlling .the pressure of that cushion of fluid.

Another object of this invention is the provision of a method and system for determining and controlling the magnitude of the driving force being exerted on a pile by ascertaining the pressure values of a cushion of pressurized fluid trapped beneath the massive piston weight and regulating said pressure values in response to the determination.

A further feature of the present invention lies in the ability of the method and system provided to permit automatic control of the magnitude of a driving force being applied to a pile in response to a determination of that magnitude.

In accordance with one aspect of the present invention there is provided a regulated feeding of pressurized fluid into a bounce chamber beneath a massive piston weight to cause the piston weight to bounce up and down upon pressurized fluid in the chamber having controlled pressure. The pressure values of the pressurized fluid cushion within the bounce chamber are determined and additional pressurized fluid is controllably injected therein in response to the pressure value determination. Thus, the thrust generated by the bouncing piston weight is controlled with the result that the magnitude of the driving force being exerted on the pile is regulated also. In this manner the magnitude of the driving force applied to the pile being driven is ascertainable and controllable within predetermined desired limits.

This effective means and method of control finds particular utility in the pile driver described in my above referred to co-pending application, the description of which is incorporated herein by reference.

The various features, aspects and advantages of the controllable force pile driving method and system of the present invention will become more fully understood from a consideration of the following detailed description of embodiments of the invention, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a side elevational view of a pile driving valve and pressure gauge means for sensing pressures occuring in the bounce chamber and pressurized fluid feed means including a pressure regulator for controllably introducing pressurized fluid into the bounce chamber;

FIG. 3 is a vertical axial sectional view similar to that of FIG. 2 showing, however, a pressure controller system which automatically controllably regulates the feeding of pressurized fluid to the bounce chamber in response to a determination of pressure in the bounce chamber;

FIG. 4 is a vertical axial sectional view similar to FIGS. 2 and 3 showing, however, associated with the pile driver system, a pressure transducer for sensing the pressure in the bounce chamber and an electronic controller which controllably regulates the introduction of pressurized fluid to the bounce chamber.

Referring to FIG. 1 there is shown a pile driving system 1 comprising a transportable crane 2, a pile driver 20 and a pile 28 being driven. The pile driver is readily and conveniently transported to a construction site or the like by means of the crane 2.

The transportable crane 2 comprises a movable boom 4 which is controlled by hydraulic piston or cable means 6 both of which are mounted on the chassis 3. Also located on the chassis 3 are pressurized fluid supply 8 and an intermediate fluid reservoir 10 as well as a control panel 12. Leading from the intermediate fluid reservoir 10 which receives compressed fluid at controlled pressure from the compressed fluid supply 8 there is a flexible pressure hose line 14 which connects with the pile driver 20. Leading from the pile driver to the control panel 12 is a pressure-value transmitting line 16.

The pile driver 20 is comprised of a cylindrical housing 22 having a head plug 21 and a coupling 30 for providing desired engagement with the pile 28 being driven. The pile driver 20 is suspended from the boom 4 of the crane 2 by means of a support cable 18 secured to the head plug 21 in an appropriate manner. Also, leads (not shown) may be included for guiding the pile driver and the pile. Such leads are conventional in the industry. They are a pair of parallel vertical guide rails which are rigidly fastened to the chassis 3 and may also be fastened at their upper ends to the boom 4.

Shown being driven into the earth is a pipe pile 28, however, this is illustrative only it being understood that the present invention can be used to advantage in the driving of any type of drivable pile, such as H-beam piles, sheet piles, timber piles, pipe piles, etc. Pressurized fluid is controllably fed into the bounce chamber, in a manner to be described in more detail below, through line 14 from the pressurized fluid supply sources 8 and 10 as controlled by a regulator located on control panel 12. This control is in response to determinations of the pressure values occuring within the bounce chamber, these determinations being transmitted to instruments on the control panel 12 by means of the pressure-value transmitting line 16.

With reference to FIGS. 2-4 there is shown a pile driver method and system similar to that described and shown in my co-pending application referred to above, also embodying, however, the control method and system of the present invention. The pile driver system 20 comprises a cylinder wall 22 surrounding a cylinder 23 provided with a massive piston weight assembly,

generally indicated at 24. At the lower end of the cylinder wall 22 is a cylinder bottom assembly,

generally indicated at 26, effectively closing off the 5 lower end of the cylinder wall 22. The cylinder bottom assembly 26 includes a second piston 60 coupled to the pile 28 being driven by a detachable coupling 30 and a pile driving adaptor 32 which is shaped so as to engage the upper end of the particular pile being driven.

Within the cylinder wall 22 between the lower end of massive piston weight assembly 24 and the cylinder bottom assembly 26 is a bounce chamber 34. Pressure fluid injection means 36 are provided for suddenly injecting pressurized fluid into the bounce chamber 34 beneath the descending piston weight assembly 24. This fluid injection means 36 includes a pressurized driving fluid storage chamber 38 and a piston-actuated valve mechanism 40 which communicates with the bounce chamber 34.

The massive piston weight assembly 24 moves up and down within the cylinder 23, and it is bounced upon a cushion of pressurized fluid in the bounce chamber 34. The massive piston weight assembly 24 includes a main weight 42 of suitable massive strong material. A hearing sleeve member 44 is mounted on each end of the main weight 42 and has an annular configuration which fits onto a reduced diameter end portion 46 at the end of the weight 42, abutting an annular shoulder 48. The bearing sleeve member 44 is retained by an end cap 50 of tough hardened steel secured to the weight 42 by detachable fastening means (not illustrated). Piston rings (not shown) are provided at 54 to provide a fluid tight seal.

In the illustrated embodiment of a pile driver system as shown, the cylinder bottom assembly 26 includes a second piston 60 which is adapted to move up and down to a limited travel distance within a second cylinder 61 which is defined by a lower extension of the cylinder wall 22 below the level of the bounce chamber 34. An annular retainer and bearing element 65 defining the lower end of the cylinder 61 is secured to a mounting ring 69 which is welded to the exterior of the cylinder wall 22. At the lower end of the second piston 60, there is a coupling flange 71 adapted to be gripped by the detachable coupling 30. The detachable coupling 30 is formed by two semi-circular clamps with protruding mating flanges properly secured together.

The fluid injection means 36, including the driving fluid chamber 38 and the valve mechanism 40, injects pressurized fluid through an injection port 62 into the bounce chamber 34 beneath the descending piston weight assembly 24. The injection of the pressurized fluid by the valve mechanism 40 is actuated by the piston weight 24, by means of an upwardly extending actuator 91. The actuator 91 is equipped at its upper end with pressurized fluid trapping means 93 in the form of a large cylindrical plunger. This plunger 93 can be depressed to flt snuggly into the port 62 to trap pressurized fluid in the bounce chamber 34 after the fluid has been injected into the bounce chamber.

The pressurized fluid is supplied from a suitable source such as the supply storage tank 8, mounted on the chassis 3 (FIG. 1), of an air compressor. The compressed fluid such as air, is at a suitable pressure, for example, such as 80 lbs. per square inch (psi) to 3,000

psi.

The pressurized fluid is fed to the pile driver system through a flexible or rigid, depending on the application. pressure hose line 14 and through a connection fitting 96 (FIG. 2). This fitting 96 feeds into a passage which communicates with a bore 72 within the driving fluid chamber 38. The pressurized fluid flows from the bore 72 through openings 73 into the driving fluid chamber 38, and when the piston weight 42 depresses the plunger 91 the fluid is injected through the port 62 into the bounce chamber 34. After the piston weight 24 has bounced upwardly from the cushion of pressurized fluid, the expanded pressure fluid is released from the cylinder 23 through a plurality of outlet ports 106 in the cylinder wall 22. The air outlet ports 106 communicate with an annual muffler chamber 108.

After the expanded pressure fluid in the bounce chamber 34 has been released through ports 106 the pressure beneath the piston weight 24 is reduced allowing the piston weight to fall. When the descending piston weight again depresses the actuator 91, the valve 40 becomes suddenly opened again to inject additional pressure fluid from the storage chamber 38 into the bounce chamber 34. Thus, the descending piston weight 24 is decelerated and is accelerated upwardly once more and rises up beyond the ports 106. The expanded fluid is again released and the piston weight falls down again. If the reader desires more information concerning the pile driver 20, he may refer to said copending application.

In these repeated cycles of operation, as the massive piston weight assembly 24 continues to move up and down within the cylinder 23, it bounces upon a cushion of pressurized fluid in the bounce chamber 34, into which the pressurized fluid in accordance with the present invention is controllably injected as a function of the pressures occurring in the bounce chamber. The many advantages which accrue therefrom as indicated in the introduction will be described further below.

Communicating with the bounce chamber 34 through a sensing port 110 is a check valve 112. The downstream or exit side of this check valve 112 is connected by means of a pressure-valve transmitting line 16 to a pressure gauge 114 mounted on the instrument panel 12. The pressure value transmitting line 16 terminates at a point downstream of the pressure gauge 114 and has interposed between its termination point and the pressure gauge 114 a shut-off and bleed valve 116.

To determine the pressure values occurring during each cycle within the bounce chamber 34 the shut-off bleed valve 1 16 is closed. As the piston weight 42 compresses pressurized fluid in the bounce chamber the check valve is forced open, permitting the pressure to be transmitted to the pressure gauge 114 and to register thereon a reading of the peak pressure value occurring within the bounce chamber during that cycle. As piston weight 42 moves upward the check valve closes to retain the peak value reading on the meter 114. If higher pressure values are anticipated in the bounce chamber 34 during successive cycles, the shut-off bleed valve 116 may be kept closed since the successively higher peak pressures will be registered on the gauge 114.

This determination of the peak pressure values occurring in bounce chamber 34 provides an indication of the thrust generated by the bouncing piston weight 24 and being applied through piston 60 to the pile 28 being driven. As a result, the operator can determine the magnitude of the driving force being exerted on the pile as it is being driven. 5 As the pile 28 is driven deeper into the earth, its impedance,i.e. resistance to being driven further, usually increases. The result is to cause an increase in the peak pressure values occurring in the bounce chamber 34. The check valve 112 serves to hold this peak pressure, and the gauge 114 measures what peak pressure is occurring, as the pile driving proceeds.

By multiplying this peak pressure reading times the cross-sectional area of the cylinder bottom assembly 26, the engineering personnel who are supervising and driving job can calculate the peak value of the driving force in pounds or in tons being applied to the top of the pile. If desired, the gauge 114 can be calibrated to read directly in units of force, such as pounds or tons.

Occassionally as a pile is being driven it encounters softer or muddy strata which cause a reduction in friction and enable the pile to be driven with less impedance. Under such circumstances the pile advances farther with each thrust, and the peak pressure values occurring in the bounce chamber 34 become reduced during such easier driving cycles. The operator or supervisor who is observing the thrust gauge 114 will notice that the pointer 115 is no longer rising. He thereupon opens the shut-off bleed valve 1 16 slightly so as to bleed off some of the pressurized fluid trapped in the pressure transmitting line 116 and in the gauge 114 so that the pressure therein falls until the new values of peak pressure (or force) are indicated by the pointer 115.

If the driving force is then considered to be lower than desired, the operator can increase the driving force applied during each cycle by increasing the pressure in the pile driver storage chamber 38 and hence in the bounce chamber 34. In this way the operator can keep the driving force at the optimum value for the most effective and efficient pile driving in the least time.

Conversely, if during the driving operation the pile encounters unexpectedly large impedance, the pile will advance very little during each driving cycle. The peak pressures in the bounce chamber 34 will increase, as will be indicated by the gauge 114. If the driving force is nearing the predetermined maximum, the operator can decrease the driving force applied during each cycle. In this way the maximum force on the pile is not exceeded.

Also, by keeping a record of the amount of driving force applied at the different levels as the driving proceeds, the engineers can obtain further information about the various strata surrounding the pile.

The meter 114 may be provided with a manually adjustable pointer or index 117 which is pre-set to a position corresponding with the maximum desired force to be applied to the pile. This pre-set index 117 is adjacent to an arcuate graduated scale 119 calibrated in units of force so as to provide a convenient reference for the operator to observe. This reference scale 119 can be removable to be replaced by a different scale when a pile driver 20 having a larger or smaller diameter lower piston assembly 26, 60 is used. By this expedient the same gauge 114 can be used(calibrated in pressure)for various sizes of pile drivers 20, and the scale 119 is changed for different sizes of drivers.

The control of the driving force in the embodiment shown in FIG. 2 is carried out in response to the reading obtained on the gauge 114. As described above, pressurized fluid is introduced into the bounce chamber 34 by the valve 40 from the fluid storage chamber 38 which receives the pressure fluid from a pressurized fluid supply via the pressure hose line 14. The pressurized fluid supply may include an air compressor as seen in FIG. 1 at 9 having a receiver or reservoir tank 8. Downstream of the pressurized fluid supply 8 is a shut-off valve 118 and downstream of this shutoff valve 118 is a pressure regulator 120 having a manually adjustable handle 121, the adjustment of which controls the pressure of the fluid temporarily stored in the intermediate air reservoir 10. This intermediate fluid reservoir 10 has a capacity substantially greater than the driving fluid chamber 38. The purpose of this intermediate reservoir 10 is to assure that the pressure being introduced into the chamber 38 is substantially equivalent to the setting of the regulator 120. The intermediate fluid reservoir 10 also assures a steady pressure. Immediately downstream of the reservoir 10 is another shut-off valve 122. In normal driving operation both shut-off valves 118 and 122 are fully open. The line 14 should have a sufficiently large inside diameter to minimize pressure drop in this line.

For purposes of illustrating the manner in which the force delivered to the pile top is controlled, it is assumed by way of example, that the maximum desired force to be delivered to the top of the pile 28 corresponds with a maximum peak pressure in the bounce chamber 34 of, for example, 2000 psi. As the pile driving operation begins, the peak pressure values occurring in the bounce chamber 34 are registered on gauge 114 and are observed. If at first the pile encounters little resistance and is easily driven, the pressure values will remain comparatively low, with readings occurring of, say, 500 psi. Therefore, the operator knows that he can obtain greater thrust and more rapid and efficient driving rate into the earth by raising the peak pressure occurring in the bounce chamber 34 to correspond approximately to the allowable force desired on the pile 28.

By proper manual adjustment of the pressure regulator 120 higher pressure fluid is introduced into the intermediate reservoir 10 and thus into chamber 38, to obtain a greater thrust, and the subsequent pressure value reading is observed on the pressure gauge 114. Operation of the pile driver is then continued within the desired range of pressure values close to but under the maximum allowable pressure, namely, 2000 psi. Should the pile suddenly encounter resistance so that it is more difficult to drive, the pressure values in the bounce chamber 34 will correspondingly increase. If it is observed that the peak values occurring therein, as registered on the gauge 114, begin to approximate the maximum allowable value of 2000 psi, the pressure regulator 120 is adjusted to reduce the pressure that will flow into the fluid storage chamber 38 and thence into the bounce chamber 34. Since a maximum pressure has registered on the gauge 114, the bleed valve 116 will now have to be opened to relieve the pressure in the line 16. The pressure in the bounce chamber 34 having been reduced, the thrust delivered through the piston 60 to the top of pile 28 will be reduced also.

In the above manner, therefore, the operator determines the magnitude of the driving force being exerted on the pile by measuring the peak pressure values occurring in the bounce chamber 34 and controls this driving force by increasing or decreasing the pressure of the fluid introduced into the bounce chamber 34 in accordance with the pressure value reading obtained. Thus, when the pile is relatively easy to drive the operator increases the pressure being fed into the storage chamber 38 and obtains more efficient operation by assuring that every bounce of the piston weight will result in a greater penetration of the pile. On the other hand when the pile becomes hard to drive and the pressure values in bounce chamber 34 increase with the resulting increase in driving force exerted on the pile, the pressure is cut back to reduce this driving force and thus to prevent damage of the pile due to exceeding its maximum allowable force.

In the embodiment shown in FIG. 2, the pressure is controlled manually in response to observation of the pressure of force value reading of the gauge 114 and force index scale 119.

FIG. 3, however, shows another embodiment of the invention wherein the pressure value occurring in the bounce chamber 34 is transmitted via pressure-value transmitting line 16 to a pressure indicator-controller 124. The pressure indicator-controller 124 includes a manually adjustable means 126 whereby the maximum allowable pressure permissible in the bounce chamber 34, determined as a consideration of the maximum allowable force permitted on the pile 28, may be set as indicated by an index pointer 128. The pressures occurring in the bounce chamber 34 are registered by an indicating pointer 130. In response thereto the controller sends a signal, via lines 132 to a slave 134, such as a servo motor or pneumatic actuator, which automatically operates the pressure regulator in response to the controller 124. In a similar manner a slave 136 operates the bleed valve 116, receiving control signals via the lines 138. The signal from the pressure indicator-controller to the slaves may be either pneumatic or electrical.

In any case, the controller 124 reads the peak pressure values occurring in the bounce chamber 34, compares them with the maximum allowable pre-set value, as illustrated by pointer 128, and allows higher or lower pressure fluid into the storage chamber 38 by control of the slave 134 and pressure regulator 120 in the pressure hose line 16. When the bounce chamber pressure values reach a high, the controller sends a signal to slave 136 to open bleed valve 116. Thus, the embodiment in FIG. 3 accomplishes automatic control of the magnitude of the driving force exerted on the pile 28.

Shown in FIG. 4 is yet another embodiment of a method and system whereby the magnitude of the driving force exerted on a pile is automatically determined and used to control the driving operation. Illustrated in FIG. 4 is a pressure transducer 140 for ascertaining the pressure values occurring within the bounce chamber 34. The pressure transducer converts the pressure value reading into electrical signals which are transmitted via electrical lines 142 to an electronic controller 144. The electronic controller 144 is pre-adjusted to compare the signal corresponding to pressure values occurring in the bounce chamber 34 with a predetermined value set by pre-set means 126, shown as a control knob, as a function of the maximum force desired to be exerted on the pile. In response to this comparison the electronic controller sends a signal via lines 143 to a slave 146 which controls the pressure regulator 120 and lets greater or lesser pressure into the fluid storage chamber'38 and from there into the bounce chamber 34, as in the other embodiments.

An advantage of the embodiment according to FIG. 4 is that the controller is adjusted to the pre-determined pressure or force setting desired and the controller may be placed fairly remote from the pile driver itself such as in the cab of the crane or at a convenient remote location on the ground. The transducer provides an instantaneous determination of the pressure values, and with appropriate selection of the electronic controller one may regulate the thrust in response to either average, mean or peak pressure values. The supervising engineer can control the force being delivered during the pile driving operation, if he wishes, independent of the person who is operating the pile driver.

Thus, there has been provided a method and system whereby one can ascertain the magnitude of the driving force applied to a pile and control such driving force so as to not exceed a predetermined value. According to the illustrated embodiments of the invention, such may be done by an operator observing the pressure gauge readings of pressure values occurring in the bounce chamber of the pile driver and manually regulating a pressure regulator in response thereto to feed fluid of increased or decreased pressure to the pile driver. The same control may be obtained automatically with a variety of pressure sensing and controller devices and is in no way limited to those specifically described. An important advantage shown by obtainment of such control is increased efficiency and economy in driving piles resulting from utilization of the maximum allowable effort when a pile is relatively easy to drive and by the fact that when a pile is difficult to drive damaging results from excess force will not be delivered to it, this avoiding damage to the pile. This latter feature results in great safety of operation also. Another important advantage of the present invention is that it enables the pile to be actually driven up to a maximum force equal to the desired predetermined terminal driving force. This terminal driving force is pre-determined to be comparable to the load which the pile is intended to support when it is in service plus a factor of safety as determined by the construction engineer. In addition a running record or log of the force being exerted on the pile at each level and of the driving action occurring will provide the supervising engineer with additional information about the strata being penetrated by the pile.

What Is claimed ls:

1. A method for controllably driving an elongated, substantially rigid object such as a pile into the earth comprising the steps of:

providing a cylinder having a piston weight therein movable up and down within the cylinder, providing a gas entraping chamber in the cylinder beneath the piston weight,

intermittently feeding pressurized fluid into the chamber to cause the piston weight to bounce up and down upon pressurized fluid in said chamber,

coupling the thrust generated by the bouncing piston weight to the elongated object for exerting driving force on the object to drive it into the earth,

determining the magnitude of the driving force being exerted on the object during the bouncing of the piston weight, and

controlling the flow of pressurized fluid into said chamber in response to said determination to regulate the pressure occurring therein, thereby controlling the magnitude of the driving force being exerted on the object being driven.

2. A method for controllably driving an elongate, substantially rigid object into a yieldably material such as the earth or the like as claimed in claim 1 in which the magnitude of the force delivered to the object is determined by sensing the pressure values occurring in said chamber beneath the piston weight upon each bouncing movement of the piston weight.

3. A method for controllably driving an elongate, substantially rigid object into a yieldable material such as the earth or the like as claimed in claim 2 wherein the sensed pressure values are peak pressure values and the pressure being regulated in the gas entraping chamber is the peak pressure occurring therein.

4. A method for controllably driving an elongated, substantially rigid object such as a pile into the earth, as claimed in Claim 1, including the step of adjusting the flow of pressurized fluid to provide a maximum driving force at the termination of the driving operation equal to a pre-determined desired terminal value of driving force.

5. A method for controllably driving a pile into the earth comprising the steps of:

providing a cylinder having a massive piston weight therein movable up and down within the cylinder, providing a bounce chamber in the cylinder beneath the massive piston weight,

intermittently feeding pressurized fluid into the bounce chamber to cause the massive piston weight to bounce up and down upon pressurized fluid in the bounce chamber, coupling the thrust generated by the bouncing piston weight to the pile for driving the pile into the earth,

determining the magnitude of the thrust being generated during the bouncing of the piston weight, and

controlling the flow of pressurized fluid into the bounce chamber in response to said determination to regulate the pressure occurring therein, thereby controlling the magnitude of the driving force being delivered to the pile being driven.

6. A method for controllably driving a pile into the earth comprising the steps of:

providing a cylinder having a massive piston weight therein movable up and down within the cylinder, providing a bounce chamber in the cylinder beneath the massive piston weight,

intermittently feeding pressurized fluid into the bounce chamber for causing the massive piston weight to bounce up and down upon pressurized fluid in the bounce chamber,

coupling the thrust generated by the bouncing piston weight to the pile for exerting driving force for driving the pile into the earth,

sensing the pressure values occurring in the bounce chamber upon the bouncing movement of the massive piston weight for determining the magnitude of the force being delivered to the pile, and

controlling the flow of pressurized fluid into the bounce chamber in response to said determination to control the peak pressures occurring therein and thereby controlling the driving force being applied to the top of the pile to obtain the most efficient driving mode without exceeding the maximum desired stress on the pile.

7. A method for controllably driving a pile into the earth as claimed in claim 6 wherein the sensed pressure values are peak pressure values.

8. A method for controllably driving a pile into the earth as claimed in claim 7 wherein the peak pressure values occurring are temporarily held after they have occurred for gauging the peak pressure values.

9. A method of controllably driving a pile into the earth comprising the steps of bouncing a mass up and down upon a cushion of compressible pressurized fluid, determining the pressure values of said pressurized fluid cushion, controllably injecting additional pressurized fluid into the cushion beneath the mass in response to the pressure value determination, and controllably utilizing the downward thrust in the cushion of compressible fluid for driving the pile.

10. In a system for controllably driving an elongate substantially rigid object such as a pile into the earth including a driver having a cylinder with a piston weight of large mass reciprocatably within it, a gas entraping chamber in the cylinder beneath the piston weight, means for coupling the driver to the object being driven to transmit the thrust generated by the bouncing piston weight to the object, and means for determining the magnitude of the driving force being delivered to the object, and the further invention comprising means for controllably feeding pressurized fluid into the chamber in response to said determination to cause the piston weight to bounce upon controlled values of pressurized fluid in the chamber, for controlling the driving force applied to said object as it is being driven.

11. In a system for controllably driving an elongate substantially rigid object into a yieldably material such as the earth or the like, as claimed in claim 10, the means for determining the magnitude of the driving force being applied to the object including means for sensing the peak pressure values occurring in the gas entraping chamber.

12. In a system for controllably driving a pile into the earth including a piston weight of large mass adapted to reciprocate up and down within a cylinder, said cylinder having a second piston adapted to reciprocate up and down within the lower end of the cylinder and adapted to be coupled in thrust transmitting relationship to the pile being driven, said piston weight and second piston defining a bounce chamber between them, means for introducing pressurizes fluid into the bouncing chamber, the further invention comprising means for determining the magnitude of the driving force being delivered by the second piston to the pile during the bouncing action, and means for controlling the pressure of the pressurized fluid being introduced into the bounce chamber controlling the magnitude of the driving force being applied to the pile being driven.

13. In a system for controllably driving a pile into the earth as claimed in claim 12, the means for determining the magnitude of the driving force being delivered to the pile including means for sensing the peak pressure values occurring in the bounce chamber.

14. In a system for controllably driving a pile into the earth as claimed in claim 13, the pressure sensing means including a check valve and a pressure gauge.

15. In a system for controllably driving a pile into the earth as claimed in claim 13, the pressure sensing means being a pressure transducer.

16. In a system for controllably driving a pile into the earth including a cylinder wall defining a cylinder, a massive piston weight movably up and down within said cylinder wall and positioned below said piston weight adapted to be coupled in thrust transmitting relationship to the pile to be driven, said piston weight and cylinder bottom assembly defining a bounce chamber between them, compressible pressurized fluid storage chamber means adapted to communicate with said bounce chamber, the further invention comprising means for determining the pressure values of the fluid in the bounce chamber, a valve for blocking communication between said storage chamber and said bounce chamber, input means for controllably feeding pressurized fluid into said storage chamber from a remote source of supply in response to said determination, and means for opening said valve for injecting pressurized fluid from said storage chamber into said bounce chamber when the piston weight is descending within the cylinder.

17. In a system for controllably driving a pile into the earth as claimed in claim 16, the pressure value determining means including a pressure gauge communicating with the bounce chamber through a conduit containing a check valve so that the peak pressure valves in said bounce chamber are registered on the gauge;

18. In a system for controllably driving a pile into the earth as claimed in claim 16, the pressure valve determining means including a transducer in communication with the bounce chamber which senses the pressure values in the chamber and transforming the same into a function of an electrical signal which registers as a reading on an indicator.

19. In a system for controllably driving a pile into the earth as claimed in claim 18, further including a means for automatically regulating the input means for controllably feeding pressurized fluid into the storage chamber as a predetermined response to the determination of the pressure valves of the fluid in the bounce chamber.

20. In a system for controllably driving a pile into the earth including a pile driver coupled to the pile in a force transmitting relationship and including a massive piston weight reciprocable within a cylinder to bounce up and down on pressurized fluid in a bounce chamber, the further invention comprising means for determining the magnitude of the force transmitted to the pile by sensing the pressurized fluid pressure values occurring in the bounce chamber, means for communicating the sensed pressure value to an observer, a compressed gas supply means, an intermediate reservoir, and means for controllably feeding pressurized fluid into the bounce chamber in functional response to the determinations of the pressure values in the bounce chamber. 

1. A method for controllably driving an elongated, substantially rigid object such as a pile into the earth comprising the steps of: providing a cylinder having a piston weight therein movable up and down within the cylinder, providing a gas entraping chamber in the cylinder beneath the piston weight, intermittently feeding pressurized fluid into the chamber to cause the piston weight to bounce up and down upon pressurized fluid in said chamber, coupling the thrust generAted by the bouncing piston weight to the elongated object for exerting driving force on the object to drive it into the earth, determining the magnitude of the driving force being exerted on the object during the bouncing of the piston weight, and controlling the flow of pressurized fluid into said chamber in response to said determination to regulate the pressure occurring therein, thereby controlling the magnitude of the driving force being exerted on the object being driven.
 2. A method for controllably driving an elongate, substantially rigid object into a yieldably material such as the earth or the like as claimed in claim 1 in which the magnitude of the force delivered to the object is determined by sensing the pressure values occurring in said chamber beneath the piston weight upon each bouncing movement of the piston weight.
 3. A method for controllably driving an elongate, substantially rigid object into a yieldable material such as the earth or the like as claimed in claim 2 wherein the sensed pressure values are peak pressure values and the pressure being regulated in the gas entraping chamber is the peak pressure occurring therein.
 4. A method for controllably driving an elongated, substantially rigid object such as a pile into the earth, as claimed in Claim 1, including the step of adjusting the flow of pressurized fluid to provide a maximum driving force at the termination of the driving operation equal to a pre-determined desired terminal value of driving force.
 5. A method for controllably driving a pile into the earth comprising the steps of: providing a cylinder having a massive piston weight therein movable up and down within the cylinder, providing a bounce chamber in the cylinder beneath the massive piston weight, intermittently feeding pressurized fluid into the bounce chamber to cause the massive piston weight to bounce up and down upon pressurized fluid in the bounce chamber, coupling the thrust generated by the bouncing piston weight to the pile for driving the pile into the earth, determining the magnitude of the thrust being generated during the bouncing of the piston weight, and controlling the flow of pressurized fluid into the bounce chamber in response to said determination to regulate the pressure occurring therein, thereby controlling the magnitude of the driving force being delivered to the pile being driven.
 6. A method for controllably driving a pile into the earth comprising the steps of: providing a cylinder having a massive piston weight therein movable up and down within the cylinder, providing a bounce chamber in the cylinder beneath the massive piston weight, intermittently feeding pressurized fluid into the bounce chamber for causing the massive piston weight to bounce up and down upon pressurized fluid in the bounce chamber, coupling the thrust generated by the bouncing piston weight to the pile for exerting driving force for driving the pile into the earth, sensing the pressure values occurring in the bounce chamber upon the bouncing movement of the massive piston weight for determining the magnitude of the force being delivered to the pile, and controlling the flow of pressurized fluid into the bounce chamber in response to said determination to control the peak pressures occurring therein and thereby controlling the driving force being applied to the top of the pile to obtain the most efficient driving mode without exceeding the maximum desired stress on the pile.
 7. A method for controllably driving a pile into the earth as claimed in claim 6 wherein the sensed pressure values are peak pressure values.
 8. A method for controllably driving a pile into the earth as claimed in claim 7 wherein the peak pressure values occurring are temporarily held after they have occurred for gauging the peak pressure values.
 9. A method of controllably driving a pile into the earth comprising the steps of bouncing a mass up and down upon a cushion of comprEssible pressurized fluid, determining the pressure values of said pressurized fluid cushion, controllably injecting additional pressurized fluid into the cushion beneath the mass in response to the pressure value determination, and controllably utilizing the downward thrust in the cushion of compressible fluid for driving the pile.
 10. In a system for controllably driving an elongate substantially rigid object such as a pile into the earth including a driver having a cylinder with a piston weight of large mass reciprocatably within it, a gas entraping chamber in the cylinder beneath the piston weight, means for coupling the driver to the object being driven to transmit the thrust generated by the bouncing piston weight to the object, and means for determining the magnitude of the driving force being delivered to the object, and the further invention comprising means for controllably feeding pressurized fluid into the chamber in response to said determination to cause the piston weight to bounce upon controlled values of pressurized fluid in the chamber, for controlling the driving force applied to said object as it is being driven.
 11. In a system for controllably driving an elongate substantially rigid object into a yieldably material such as the earth or the like, as claimed in claim 10, the means for determining the magnitude of the driving force being applied to the object including means for sensing the peak pressure values occurring in the gas entraping chamber.
 12. In a system for controllably driving a pile into the earth including a piston weight of large mass adapted to reciprocate up and down within a cylinder, said cylinder having a second piston adapted to reciprocate up and down within the lower end of the cylinder and adapted to be coupled in thrust transmitting relationship to the pile being driven, said piston weight and second piston defining a bounce chamber between them, means for introducing pressurizes fluid into the bouncing chamber, the further invention comprising means for determining the magnitude of the driving force being delivered by the second piston to the pile during the bouncing action, and means for controlling the pressure of the pressurized fluid being introduced into the bounce chamber controlling the magnitude of the driving force being applied to the pile being driven.
 13. In a system for controllably driving a pile into the earth as claimed in claim 12, the means for determining the magnitude of the driving force being delivered to the pile including means for sensing the peak pressure values occurring in the bounce chamber.
 14. In a system for controllably driving a pile into the earth as claimed in claim 13, the pressure sensing means including a check valve and a pressure gauge.
 15. In a system for controllably driving a pile into the earth as claimed in claim 13, the pressure sensing means being a pressure transducer.
 16. In a system for controllably driving a pile into the earth including a cylinder wall defining a cylinder, a massive piston weight movably up and down within said cylinder wall and positioned below said piston weight adapted to be coupled in thrust transmitting relationship to the pile to be driven, said piston weight and cylinder bottom assembly defining a bounce chamber between them, compressible pressurized fluid storage chamber means adapted to communicate with said bounce chamber, the further invention comprising means for determining the pressure values of the fluid in the bounce chamber, a valve for blocking communication between said storage chamber and said bounce chamber, input means for controllably feeding pressurized fluid into said storage chamber from a remote source of supply in response to said determination, and means for opening said valve for injecting pressurized fluid from said storage chamber into said bounce chamber when the piston weight is descending within the cylinder.
 17. In a system for controllably driving a pile into the earth as claimed in claim 16, the preSsure value determining means including a pressure gauge communicating with the bounce chamber through a conduit containing a check valve so that the peak pressure valves in said bounce chamber are registered on the gauge.
 18. In a system for controllably driving a pile into the earth as claimed in claim 16, the pressure valve determining means including a transducer in communication with the bounce chamber which senses the pressure values in the chamber and transforming the same into a function of an electrical signal which registers as a reading on an indicator.
 19. In a system for controllably driving a pile into the earth as claimed in claim 18, further including a means for automatically regulating the input means for controllably feeding pressurized fluid into the storage chamber as a predetermined response to the determination of the pressure valves of the fluid in the bounce chamber.
 20. In a system for controllably driving a pile into the earth including a pile driver coupled to the pile in a force transmitting relationship and including a massive piston weight reciprocable within a cylinder to bounce up and down on pressurized fluid in a bounce chamber, the further invention comprising means for determining the magnitude of the force transmitted to the pile by sensing the pressurized fluid pressure values occurring in the bounce chamber, means for communicating the sensed pressure value to an observer, a compressed gas supply means, an intermediate reservoir, and means for controllably feeding pressurized fluid into the bounce chamber in functional response to the determinations of the pressure values in the bounce chamber.
 21. In a system for controllably driving a pile into the earth as claimed in claim 20, further including means for automatically regulating the feeding of pressurized fluid as a predetermined function of the bounce chamber pressure value. 